The present invention relates to spatial light modulator displays and more specifically to improving the performance of such displays by increasing the thermal dissipation properties of the spatial light modulator.
Digital spatial light modulators (SLM) are revolutionizing projection display products. For example, digital micromirror device (DMD(trademark), a type of SLM) projectors are available in SVGA, XGA, and HDTV resolutions. These small, lightweight, projectors provide extremely sharp, high-quality pictures. Liquid crystal displays (LCD) technology offer similar results.
One of the biggest problems associated with these projectors is that of dissipating the heat from the SLM, caused largely by the very bright light focused on the surface of the small device. The SLM also must dissipate heat generated from electrical operation of the device, although at a much lower level. For high performance and long life, these small thumbnail sized devices must be able to dissipate the large amount of heat, which is generated by the combination of incoming light flux on its surface and electrical operation internal to the device.
Typically in DMD displays, heat sinks are attached to the devices to mitigate and control the temperature properties of the system. A stud is bonded to the back surface of the DMD package with an epoxy or double-sided tape. The stud is then attached with fasteners to a heat sink to create a thermal path for removing heat from the device. This is a labor-intensive process and has proven to be a major concern relative to the high-performance and reliability of the system. The studs can break off due to inconsistency from batch-to-batch of the epoxy patch material used in attaching them. There can also be inherent variations in the bonding process, assembly, curing, holding force, and other process complexities. All of these complications, which often result in returned product, tend to drive up the system cost.
What is needed is a method that eliminates the stud, heat sink, and fasteners and provides an optimal path for removing heat from the device(s). The method of the present invention accomplishes this by making the SLM socket out of a thermally conductive material and having it encapsulate the device package, making positive contact with the package perimeter. This socket/heat sink combination is then clamped to a copper plane on a printed wiring board (PWB) to effectively remove the heat from the SLM. Since this socket/heat sink wraps around the device, covering the front edges around the cover glass of the device package, this directly addresses the removal of excessive heat generated by the optical flux applied to the surface of the device.
This invention discloses a method for removing heat from a SLM device in a digital projection display by encapsulating the device in a thermal conductive socket attached to a PWB. The socket wraps around the device package to remove both optically generated heat from the front of the device and electrically generated heat within the device. The socket is in positive thermal contact with the perimeter of the device with the gap at the interface to the PWB being also filled with a conductive medium. A connectivity interposer element is inserted between the bottom of the device and the PWB for electrical connection to the device. In higher brightness projector applications, fins are added to the socket to increase the mass and surface area of the socket, thereby improving the heat dissipation properties of the system. The heat sink socket is attached to the PWB using a screw attachment means. As the device is attached to the PWB, the applied pressure causes the interposer element to make electrical contact between the PWB and SLM device.
This approach completely eliminates conventional heat sinks, mounting studs, and fasteners, which tend to be low-yield, and high-cost items in fabricating a projection display. The problem of the heat sink stub breaking off and causing the display to fail is eliminated by this method. The fail-safe approach of this invention positions, aligns, clamps, and heat sinks the SLM in a straightforward manner to provide a high-performance, long-life projection system.